The present invention relates to a programmable sequence controller (hereinbelow, simply termed `PSC`) which functions to display the input/output statuses of signals.
There have been often used PSCs furnished with the display function for displaying the input/output statuses of signals in order to do an error check of a user program or to inquire into the cause of a malfunction. The PSCs have heretofore been proposed in, for example, Japanese patent applications laid-open No. 58-132809, No. 58-94011 and No. 58-78207.
Many of the hitherto-proposed PSCs with the display function have indicator lamp units mounted on the casings of the so-called input/output modules having signal input terminals and signal output terminals. It is therefore impossible to comply with a request for fulfilling the display function at a position remote from the input/output modules.
The number of indicator lamps to be prepared is equal to the number of signal input and output nodes on many occasions. In general, the number of the input/output nodes of a single input/output module is 8.times.n (n being a positive integer), and hence, the number of the indicator lamps becomes considerably large. Accordingly, where the indicator lamps are installed poses a problem.
It is dangerous for people to come into contact with input/output terminals. Therefore, insulating covers for concealing the terminals are required.